Wiring at breaker. 3 wire down to 2?

[vwtrey]

I’m going to have an electrician do this because I don’t know how, but I’d like to understand more. I’m really stupid with electrical work.

The far right breaker is a 3 wire. I want to use that breaker to go to my air compressor. The plan is to hardwire to the compressor with a safety switch in between.

The compressor is two wire. How will this work, or what’s a good way of doing it? I brought a roll of 6/2 hoping it would be straight forward, but when I saw 6/3, I knew it would be beyond my knowledge.

 

[The Cobbler]

3 wire has a neutral, needed for 240/120 volt applications like stoves & driers.
2 wire does not have a neutral and supplies only 240 volts like welders, air compressors, etc

 

[vwtrey]

3 wire has a neutral, needed for 240/120 volt applications like stoves & driers.
2 wire does not have a neutral and supplies only 240 volts like welders, air compressors, etc

Does it require a different breaker, or just get left off using the existing one?

 

[Cruzan80]

What I think you are saying is the wires that are connected to the far right breaker at the junction box are Red/Black/White/Ground. And your compressor only needs Red/Black/Ground.

If that is what you are saying, it is fine to connect the Red/Black/Ground, and leave the white wire disconnected. This would be for the neutral, which is only needed for a 120/240 connection (as mentioned above).

I am saying Ground instead of Green, as it is possible to see a bare ground in the run, and didn't want to confuse further. If it is Green, replace for Ground above.

 

[vwtrey]

What I think you are saying is the wires that are connected to the far right breaker at the junction box are Red/Black/White/Ground. And your compressor only needs Red/Black/Ground.

If that is what you are saying, it is fine to connect the Red/Black/Ground, and leave the white wire disconnected. This would be for the neutral, which is only needed for a 120/240 connection (as mentioned above).

I am saying Ground instead of Green, as it is possible to see a bare ground in the run, and didn't want to confuse further. If it is Green, replace for Ground above.

Yes, that’s what I’m trying to say.

The outlet on this breaker will need to be moved. I have a 100’ roll of 6/2 and I’m hoping the electrician can use it and remove the 6/3. That would save some money.

 

[The Cobbler]

is the 40 amp breaker what's required for your compressor? then is fine

 

[Cruzan80]

There is not a need to remove the existing wire, as long as the previous junction box is accessable. You can tie the new wire in there, and "continue" the run. Just leave the white neutral disconnected.

This assumes the run is in the same direction as the previous one. Otherwise, replacing is fine.

Edit: If the motor on the compressor is calling for a 40A breaker, it is a great idea to hardwire (I know you mentioned that was the plan). Otherwise, rated HP plugs/receptacles get pricey fast. I think if it is 100ft away, you do need a disconnect closer to meet code (unsure of max distance). This may be what you are referring to as a safety switch.

 

[vwtrey]

There is not a need to remove the existing wire, as long as the previous junction box is accessable. You can tie the new wire in there, and "continue" the run. Just leave the white neutral disconnected.

This assumes the run is in the same direction as the previous one. Otherwise, replacing is fine.

Thanks.

Why doesn’t the red wire become the extra wire in this? Like if it needed to be there for 3 wire, then black and white would be identical to 2 or 3 wire, and red would be the different leg?

 

[Cruzan80]

Common standards. THEORETICALLY Could you wire it up using white and black, and have it work? Yes, the electricity doesn't care about the outside of the wire coating. However, it is dangerous to another person, who thinks the white wire is not an incoming carrier of electricity (neutrals provide a path back only), and they could get hurt.

To your next question thinking ahead ("Can I relabel the white wire instead?"), there are times that it is allowed to re-assign wires with a wrap of tape at each end, but only at a certain size or larger (white wire, with a red tape band to denote it is really supposed to be red). I am not as familiar with code as several others on here, so I am not going to say at what point it is allowed (I just know it is a certain point).

In a circuit using only two hots and a ground, there is no connection to the neutral bar in the breaker box (the two hots go to the breaker, and the ground to the ground bar).

 

[rharman]

What am I missing here? I only see two wires on that breaker - black & red.

 

[The Cobbler]

the ground & neutral are on the bar at the top of the panel

 

[vwtrey]

Common standards. THEORETICALLY Could you wire it up using white and black, and have it work? Yes, the electricity doesn't care about the outside of the wire coating. However, it is dangerous to another person, who thinks the white wire is not an incoming carrier of electricity (neutrals provide a path back only), and they could get hurt.

To your next question thinking ahead ("Can I relabel the white wire instead?"), there are times that it is allowed to re-assign wires with a wrap of tape at each end, but only at a certain size or larger (white wire, with a red tape band to denote it is really supposed to be red). I am not as familiar with code as several others on here, so I am not going to say at what point it is allowed (I just know it is a certain point).

In a circuit using only two hots and a ground, there is no connection to the neutral bar in the breaker box (the two hots go to the breaker, and the ground to the ground bar).

So if the three wire is replaced with two wire, being black and white, red goes away, would that work but be incorrect?

I appreciate you answering these questions.

 

[Stuff]

Also have your electrician install a ground bar in the panel and move the grounds off of the neutral bar to it

 

[wyliesdiesels]

I’m going to have an electrician do this because I don’t know how, but I’d like to understand more. I’m really stupid with electrical work.

The far right breaker is a 3 wire. I want to use that breaker to go to my air compressor. The plan is to hardwire to the compressor with a safety switch in between.

the far right breaker is NOT a "3-wire" breaker. if it was then there would be an additional lug and it would be a 3 phase panel.

Its a double pole breaker for 240v branch circuit. you can use this to feed your compressor depending on the HP rating of your motor.

The compressor is two wire. How will this work, or what’s a good way of doing it? I brought a roll of 6/2 hoping it would be straight forward, but when I saw 6/3, I knew it would be beyond my knowledge.

why did you buy 6/2? what is the HP rating on the compressor motor?

 

[nadogail]

Neutral conductors are Almost Never witched or fused. There are different rules for hazardous locations.

 

[vwtrey]

the far right breaker is NOT a "3-wire" breaker. if it was then there would be an additional lug and it would be a 3 phase panel.

Its a double pole breaker for 240v branch circuit. you can use this to feed your compressor depending on the HP rating of your motor.

why did you buy 6/2? what is the HP rating on the compressor motor?

It was leftover wire from when the electrician wired it at the old house. It’s a 5hp motor.

 

[wyliesdiesels]

There is not a need to remove the existing wire, as long as the previous junction box is accessable. You can tie the new wire in there, and "continue" the run. Just leave the white neutral disconnected.

This assumes the run is in the same direction as the previous one. Otherwise, replacing is fine.

Edit: If the motor on the compressor is calling for a 40A breaker, it is a great idea to hardwire (I know you mentioned that was the plan). Otherwise, rated HP plugs/receptacles get pricey fast. I think if it is 100ft away, you do need a disconnect closer to meet code (unsure of max distance). This may be what you are referring to as a safety switch.

yes if the compressor is more than 50' from and not within sight of the electrical panel, a disconnect is required at the compressor.

 

[wyliesdiesels]

Thanks.

Why doesn’t the red wire become the extra wire in this? Like if it needed to be there for 3 wire, then black and white would be identical to 2 or 3 wire, and red would be the different leg?

Because the white is supposed to only be used for the grounded conductor (neutral). there is one exception in that a white conductor in a manufactured cable can be recolored/repurposed as am ungrounded conductor (hot) but if you already have a red conductor available, whats the point?

 

[wyliesdiesels]

Common standards. THEORETICALLY Could you wire it up using white and black, and have it work? Yes, the electricity doesn't care about the outside of the wire coating. However, it is dangerous to another person, who thinks the white wire is not an incoming carrier of electricity (neutrals provide a path back only), and they could get hurt.

To your next question thinking ahead ("Can I relabel the white wire instead?"), there are times that it is allowed to re-assign wires with a wrap of tape at each end, but only at a certain size or larger (white wire, with a red tape band to denote it is really supposed to be red). I am not as familiar with code as several others on here, so I am not going to say at what point it is allowed (I just know it is a certain point).

In a circuit using only two hots and a ground, there is no connection to the neutral bar in the breaker box (the two hots go to the breaker, and the ground to the ground bar).

size is one exception to recoloring a neutral conductor. the other one is if its in a manufactured cable such as NM-b

 

[wyliesdiesels]

Also have your electrician install a ground bar in the panel and move the grounds off of the neutral bar to it

be careful with this. if the feed is 3-wire, it needs to stay bonded. which is often the case on older panels in detached structures

it does look like its a 4-wire feed (green conductor) and so it should be converted.

@vwtrey is this panel in a detached structure from where you main panel is?

 

[vwtrey]

be careful with this. if the feed is 3-wire, it needs to stay bonded. which is often the case on older panels in detached structures

it does look like its a 4-wire feed (green conductor) and so it should be converted.

@vwtrey is this panel in a detached structure from where you main panel is?

Yes, it is a panel in another structure

 

[N_Jay]

So if the three wire is replaced with two wire, being black and white, red goes away, would that work but be incorrect?

I appreciate you answering these questions.

Correct for 110, Incorrect for 220.
Green or uninsulated is ALWAYS Ground.
White is ALMOST ALWAYS Neutral
Colors and Black are Hot, Switched, Control, etc.

(For 99% of residential)
110 is a hot and a neutral (One phase)
220 is two Hots (Two opposite (Split) phases)

 

[Cruzan80]

Thanks for stepping in Wylie. I know enough about this for the generalities, but was hoping someone like you could fill in the spots I was fuzzy on (which you did!).

 

[eegger]

Why wouldn't you leave it as is (if the wire is the correct size), when you hardwire your compressor, just cap the white neutral ? Or Cap and disconnect both ends?

 

[exranger06]

If you are replacing the old wire and running the new, 2-conductor cable from the panel all the way to the compressor: Wrap some black tape around the ends of the white wire, so everyone knows it's not being used as a neutral. Connect the black and white wire to the terminals on the breaker. At the other end, connect both wires to the terminals on the disconnect. Done.

If you are reusing some of the existing 3-conductor cable: Leave the black and red wires connected to the breaker. Leave the white neutral connected to the neutral bar. At the junction box, cap off the white wire (and DON'T wrap tape around it). Take your new 2-conductor wire, wrap tape around THAT white wire only. Connect that white wire to the existing red wire. Connect the black wires together. At the disconnect, wrap tape around the white wire, and connect both wires to the terminals on the disconnect.

White wires are supposed to be used only for neutrals, but in situations like this where you only need 2 wires, and all 2-wire cables only come with a black and white wire (no other color combinations), you're allowed to re-identify the white wire and use it as a hot leg. The old/existing 3-wire cable you have already has the "proper" black and red wires for 2 hot legs, so use them as such. Just cap off the unused neutral.

 

[wyliesdiesels]

Yes, it is a panel in another structure

Is the feeder 4-wire or 3-wire? is there other metallic pathways between the buildings (metal conduit, water line, gas line, phone line etc)?

Is there ground rods? i dont see any large solid copper wires that would go to rods

 

[wyliesdiesels]

It was leftover wire from when the electrician wired it at the old house. It’s a 5hp motor.

since its 5HP you need min #10 THWN cu or #8/2 NM-b.... it will need to be hardwired unless you use expensive pin and sleeve plugs

 

[eegger]

Doesn't he already have 6/3 run ? is the location changing ?

Wouldn't you just run #10 THWN though conduit from the compressor to the wall junction box?


Or probably best to run conduit and THWN, like this setup ?

 

[mikedodge]

Doesn't he already have 6/3 run ? is the location changing ?

Wouldn't you just run #10 THWN though conduit from the compressor to the wall junction box?


Or probably best to run conduit and THWN, like this setup ?

You typically don't run hard conduit directly to a compressor like that.

 

[wyliesdiesels]

Deleted.....

 

[wyliesdiesels]

Doesn't he already have 6/3 run ? is the location changing ?

Wouldn't you just run #10 THWN though conduit from the compressor to the wall junction box?


Or probably best to run conduit and THWN, like this setup ?

No because of vibration. You should run flex- either make your own whip with either FMC/greenfield & THWN or buy a pre-made one that uses LT. You could also use MC if you can find the correct size (#10 for 5HP).

 

[Leaflessshadetree]

BTW: Looks like the breaker in the middle has the white wire taped to "recolor" it as black (as mentioned earlier).
I'd rather keep the BK/RD and neutral the OP has. I might also install a sub panel instead of a disconnect switch.